from optparse import OptionParser
import time
import os

[...]
parser = OptionParser()
parser.add_option("-r", "--reboot", 
                  action="store_true", dest="reboot", default=False,
                  help="reboot the system")
parser.add_option("-s", "--shutdown",
                  dest="downTime", default="0",
                  help="shutdown the system")

(options, args) = parser.parse_args()

print(options.reboot)
print(options.downTime)

